docs: def _activity_helper(modifier: str, location=None):
      """Make an activity dictionary.
  
      :param str modifier:
      :param Optional[dict] location: An entity from :func:`pybel.dsl.entity`
      :rtype: dict
      """
      rv = {MODIFIER: modifier}
  
      if location:
          rv[LOCATION] = location
  
      return rv